When irrigating in agricultural or horticultural work, there is frequently a need to filter water which is to be discharged, since the water can sometimes contain large amounts of suspended matter which would otherwise block discharge orifices. In some instances the suspended matter is present in such large quantities that it is necessary to be able to quickly and easily backwash the filter, washing away debris which has been restrained as water flows through the filter. The filters which are most commonly used are the so called gauze filters and the so called sand filters.
The main object of this invention is to provide means which will effectively backwash a filter upon the pressure drop across that filter reaching a certain level, so that the backwash is automatic. It is a further object of this invention to provide means which are likely to be effective and functional under a wide range of conditions and which will require only a small amount of maintenance.